Electric switch



F. E. LUEBKERT ELECTRIC SWITCH Nov. 24, 1953 2 Sheets-Sheet 1 Filed April 6 1950 INVENTOR. FRED E. [UfB/(f/QT.

BY I Wjj ATTOPNEK F. E. LUEBKERT ELECTRIC SWITCH Nov. 24, 1953 2 Sheets-Sheet 2 Filed April 6, 1950 3 INVENTOR.

Qf FRED E. LUfBKE/W Patented Nov. 24, 1953 UNITED STATES PATENT OFFIE one-half to Maxwell E.

York, N. Y.

Sparrow, New

Application April 6, 1950, Serial N 0. 154,397

9 Claims. 1

This invention relates to improvements in electrical switches, and particularly to improvements in switches of the knife blade type for conducting large currents.

The desirability of achieving a high contact pressure between the blade of the switch and the fixed post or contact in switches having a high current carrying capacity has long been recog nized. Such high contact pressures cannot feasibly be achieved by the mere resilience of the parts; and therefore switches of the knife blade type have been constructed in which the desired contact pressure is obtained by suitable clamping structure arranged to be actuated after the mov able contact, or blade, is in the switch closed posi tion, and to be released before moving the from the closed position. Such prior switches have included a pivot post electrically connected to one of the terminals of the switch, a pair of blades pivotally disposed on opposite sides of the pivot post and engaging on opposite sides of a fixed post when in the switch closed position, and an operating member connected to the blade clamping structure and movable relative to the blade for clamping the blade on the post only when the blades are in switch closed position. When the blades are in switch open position, looking means prevent movement of the operating member relative to the blades and such operating member is then manipulated solely for the purpose of swinging the blades.- However, the devices heretofore provided for locking the operating member relative to the blades during the switch open position of the latter have all been relatively complicated, subject to mechanical breakdown, and required the exertion of excessive force in effecting the movement from locked to unlocked position.

Therefore, an object of this invention is to provide, in a relatively large current conducting switch of the knife blade type including clamping means for effecting a high contact pressure between the posts and the swinging blades when the latter are in switch closed position, improved locking devices for preventing operation of the clamping means while the blades are in open position, which locking devices are released when the blades are in switch closed position.

Another object of this invention is to provide,- in a switch of the type described, locking means for the blade clamping mechanism which is mov able from the locked to the released position by the exertion of a minimum effort on the part of the operator to thereby effect the smooth and easy movement of the switch blades.

Still another object of this invention is to provide, in a switch of the kind described, a looking assembly for the blade clamping mechanism which is so arranged and constructed as to permit the easy adjustment of the several parts thereof to insure the proper operation of the locking assembly at all times.

A further object of the invention is to provide, in a switch of the kind described, a locking assem: bly for the blade clamping mechanism which is so arranged and constructed as to permit its attachment to existing switches with a minimum of modification of the latter.

Finally, it is an object of this invention to proride, in a switch of the kind described, a locking device which is simple in construction and operation, sturdy, inexpensive to construct, and substantially foolproof in operation, to thereby permit the widest use thereof.

These and other objects and advantages will be apparent in the following detailed description and in the accompanying drawingsforming a part thereof, which description and drawings disclose a preferred illustrative embodiment of the ill-f vention with the invention consisting in the novel combination, arrangement and details of construction of the several parts disclosed therein and more particularly defined in the appended claims.

In the drawings:

Figure 1 is a side elevation of a knife blade switch in open position embodying a locking device for the blade clamping mechanism constructed according to an embodiment of this invention; I

Figure 2 is a side elevation of the switch shown in Figure 1, and illustrating the relationship of the several parts when the blades have been pivoted towards closed position, but with the blades not yet in full closed position;

Figure 3 is a fragmentary front view of a portion of the switch in the position illustrated by Figure 2, and showing the details of certain parts of the locking assembly;

Figure 4 is a side elevation of the switch illustrated in Figure 1, with the blades in full closed position, and before the clamping mechanism has been moved to blade clamping position; and

Figure 5 is a side elevation of the switch in full closed blade clamped. position.

Referring to the drawings, wherein like reference numerals indicate like parts, a well known switch of the knife blade type, having a great current carrying capacity, is generally indicated by the reference numeral Ill. The switch l0 includes a pair of terminal blocks H and I2, formed of a highly conductive material, such as copper, and mounted upon an insulating mounting board |3 in spaced apart relationship. A fixed post l4, formed of a highly conductive material, extends outwardly from the terminal block II. An arcuate slot I5 is formed in the fixed post M, and opens through the outer free edge of the latter. Stop forming blocks |3 are secured to the opposite side faces of the fixed post |4 adjacent the base thereof. A pivot post I! formed of a highly conductive material extends outwardly from the terminal block l2. Switch open stops l8 are secured to the opposite side faces of the pivot post I? adjacent the base of the latter. The movable contact of the switch Ill is formed of a pair of spaced apart, elongated, highly conductive blades l9 and 20. Each of the blades l9 and is pivotally connected adjacent one end thereof, to the pivot post H by the pivot member 2| extending therethrough. The pivot member 2| is rotatable with respect to the pivot post I1, and also relative to the blades l9 and 20. A substantially triangular operating member 22 is rotatably disposed upon the pivot member 2|. A circular disc or plate 23 is fixed upon the pivot member 2| and is interposed between the operating member 22 and the knife blade l9. Diametrically opposed pins 24 and 25 extend from the disc 23 and are loosely re ceived within the arcuate slots 26 and 2'! respec tively formed in the operating member 22, to thereby provide a lost motion connection between the operating member 22 and the pivot member 2|. An insulated handle 23 is fixed to the operating member 22 and provides means for actuating, or moving, the knife blades l9 and 23 from the open to closed position thereof, and from the closed to open position, and also provides actuating means for the blade clamping mechanism to be described hereinafter.

The blade clamping mechanism includes a shaft 29 rotatably carried by the free ends of the blades l9 and 20, and positioned to be received within the arcuate slot |5 of the fixed post when the blades are swung to closed position. A crank member 30 is fixedly attached to the shaft 29, and a connecting rod 3| is pivotally connected at its opposite ends to the operating member 22 and the crank member 36, respectively, Therefore, rocking of the operating member 22 relative to the blades l9 and 23 will effect rotation of the pivot member 2| and the shaft 29 relative to the blade. Both the pivot member 2| and the shaft 23 are formed with screw threads upon the ends thereof which extend through the knife blade 20. These threaded ends of the pivot member and the shaft are received by internally threaded members 29a, one of which is shown in Figure 3, fixed upon the outer surface of the knife blade 20. Therefore, rotation of the pivot member 2| and the shaft 23 in one direction, relative to the blades l3 and 20, will effect the drawing together of the blades for clamping upon the opposite side faces of the fixed post l4 and the pivot post ll. Rotation of the pivot member 2| and the shaft 29 in the opposite direction will effect the spreading apart of the blades l9 and 20 in order to release the engagement, or clamping, of the blades upon the posts Hi and ll, to provide for the easy swinging of the knife blades relative to the posts. The structure so far described is that of a well known switch of the knife blade type, including clamping mechanism for effecting intimate engaget ment between the knife blades and the terminal posts when the blades are in switch closed position.

This invention, which will now be described, relates to a novel locking assembly for preventing rotation of the pivot member 2! and the shaft 29 relative to the knife blades l9 and 23 in a direction which would effect drawing together of the knife blades, when the blades are in switch open position. That is, the locking mechanism constructed according to this invention is operative while the blades are in switch open position to prevent rotation of the shafts 2| and 29 in a direction which would effect drawing together of the blades. This feature of operation of the locking mechanism permits the easy movement of the blades onto the fixed post l4. The locking mechanism, forming this invention, includes a substantially cylindrical pin 32 secured to the connecting rod 3| by the nut 33, and extending laterally relative to the connecting rod so as to underlie the blade [9. A substantially triangular bell-crank is loosely disposed between the blades l9 and 20 and is pivotally carried at one corner by the pivot member 35 which secures the bellcrank to the blade I9. The edge of the bellcrank opposite to the pivoted corner thereof is cut out as at 36, and an eccentric adjusting cam 37 adjustably carried by the pin 38 on the blade i9 engages within the cut out 36 and limits the rocking of the bell-crank 34 towards the connecting rod 3|. A spring 39 fixed at one end 48 to the blade i9, and at the other end to a corner of the bell-crank 34, constantly urges the bell-crank into engagement with the surface of the eccentric cam 31. An inclined, laterally extending projection 4| extends from the corner of the bell-crank 34, removed from the pivot 35. The projection 4| is normally disposed, by reason of the spring 39 and the eccentric member 37 in a position lying in the path of travel of the pin 32 on the connecting rod 3|. That is, the projection 4| is normally in a position in which it is engageable with the pin 32 to prevent movement of the connectng rod 3| relative to the blades l9 and 20. A lock releasing member, generally referred to by the numeral 42, is carried by the insulating mounting board |3. The lock releasing member 42 includes a housing 43 secured to the board i3, and receiving a threaded bolt 44 formed with a head 45 on the outer end thereof. The lock releasing member is so disposed as to engage the head 45 with the projection 4| when the blades l9 and 20 are pivoted to closed position. A lock nut 46 is threaded upon the bolt 44 between the head 45 thereof and the housing 43 for retaining the bolt 44 in selected extended position relative to the housing.

Beginning with the switch in full open position, as illustrated in Figure 1, the projection 4| of the bell-crank 34 is engaged with the pin 32 on the connecting rod 3| and is disposed beyond the center thereof, so that swinging of the handle 28 in the direction of the arrow, for pivoting the blades about the pivot member 2|, will not rotate the operating member 22 and. the bell-crank 30 in the direction of the arrow relative to the blades I9 and 20. That is, the projection 4| and the pin 32, when engaged as shown in Figure 1, will prevent longitudinal movement of the connecting rod 3| relative to the switch blades. The position of the projection 4| with respect to the axis of the pin 32 may be adjusted by rotating the eccentric cam 37 carried by the blade l9,-

which cam is operative to change the normal position of the projection relative to the pin. The adjustment provided by the cam 37 is of great importance for it ensures the proper relative positions of the projection 4i and the pin 32 even when the parts are mass produced. Therefore, the clamping mechanism will be prevented from drawing the blades 19 and together during the movement of the blades towards the fixed post I l.

When the blades is and Zil have been pivoted towards the closed position, and have reached a point just prior to engagement of the blades with the stops it on the fixed post It, as shown in Figure 2, the head of the releasing mechanism 52 will engage the projection 4| on the bell-crank. The timing of the engagement of the head 15 with the projection 4| is determined, and may be adjusted, by the extension of the bolt t4 out of the housing Further movement of the blades iii and 2G to the full closed position, illustrated in Figure 4, will result in the rocking of the bell crank as relative to the blade it, under the influence of the relatively fixed head abutting against the projection 4 I. That is, the head 55 of the releasing mechanism t2 will move the projection t! beyond the center of the pin 32. Further movement of the handle 28 in the direction of closing of the switch, will cause the operating member 22 to rotate relative to the blades I9 and 2t and to effect longitudinal movement of the connecting rod 3! relative to the blade. Such longitudinal movement of the connecting rod 3i will no longer be resisted by the projection M of the pivoted bell-crank 32, since that prolection will now be free to ride over the surface of the pin 32. Therefore, once the head 45 of the releasing assembly has moved the bell crank 34, further rotation or movement of the handle 28 in the closing direction will effect the rotation of the operating member 22 and the crank 36 so that first the shaft 29 and then the pivot 21, by reason of the lost motion connection provided by the pins 2%, 17:5 engaging in the slots 25, El, will be rotated for clamping the blades 59 and 29 upon the opposite side surfaces of the posts I t and Il. The lost motion connection between the memer 22 and the pivot 2i facilitates the opening of the switch since the initial resistance to movement of the connecting rod 35 is presented only by the frictional forces on the shaft 28, and only after the clamping action at the ends of the blades engaging the post it has been relieved does the operator have to overcome the friction on the pivot i. In Figure 5, the switch is shown in the full closed position, following the rotation of the pivot 2i and shaft 29 relative to the blades, for clamping the blades upon the posts [4 and I7.

When it is desired to open the switch, the handle 28 is moved in the direction of the arrow in Figure 5, and such movement will initially effect rotation of the pivot 2i and shaft 29 in a clamp releasing direction, and further movement of the handle in the direction of that arrow will swing the blades i9 and 20 away from the fixed post l4. During the movement of the connecting rod 3! relative to the knife blades, in the direction for releasing the clamping assembly, the inclined surface of the projection ll on the bell-crank 34 will ride over the pin 32 carried by the connecting rod, and will assume the position relative to the pin shown in Figure 1.

From the above description of the structure of my locking assembly, and the operation thereof, it can be seen that the clamping assembly may only be actuated when the blades are in the full 6 closed position. Therefore, movement of the handle 28, when the blades are in any position other than the full closed position, will not eifect the drawing together of the blades l9 and 20, and therefore the free and easy movement of the blades is assured.

Having thus described a specific illustrative embodiment of a locking device constructed according to this invention, it is to be understood that various modifications and changes therein may be effected without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In an electric switch including a fixed contact, a cooperating contact movable into and out of engagement with said fixed contact, clamping means for exerting pressure between said contacts in the switch closed position thereof, and an operating member for said clamping means movable longitudinally relative to said movable contact in one direction to effect the clamping action of said clamping means and in the opposite direction to release the clamping action;

-, locking means for preventing movement of said operating member in said one direction when said movable contact is in switch open position comprising a fixed abutment carried by said operating member, a bell crank pivoted to said movable contact and swinging in a plane parallel to the plane of movement of the latter, said bell crank being formed with a lateral projection spaced from the axis of pivoting and movable into and out of the path of travel of said fixed abutment moving with said operating member, means constantly urging said bell crank projection into the path of travel of said abutment to prevent longitudinal movement of the latter in the direction for effecting the clamping action of said clamping means and including a spring member interposed between said bell crank and said movable contact constantly urging said bell crank to rock in the direction of movement of said movable contact in travelling to switch closed position, adjustable means carried by said movable contact and engaging said bell crank for limiting the movement of said bell crank in the spring urged direction, and lock releasing means engaging said bell crank when said movable contact is in the switch closed position and moving said bell crank projection out of the path of travel of said abutment whereby said operating member may be moved to effect the clampin action of said clamping means.

2. In an electric switch, locking means according to claim 1, wherein said bell crank is formed with a recess in the edge thereof opposite the axis of pivoting, and said adjustable mean is constituted by an eccentric cam member loosely received by said recess and rotatably mounted on said movable contact, said eccentric cam member engaging a portion of the edge of said recess to thereby limit movement of said bell crank in the spring urged direction.

3. In an electric switch, locking means according to claim 2, wherein said abutment fixed to said operating member consists of an elongated cylindrical pin extending laterally from the side of said operating member facing said bell crank.

4. In an electric switch, locking means according to claim 3, wherein said lateral projection on said bell crank is inclined relative to the path of travel of said cylindrical pin with said operating member so that said projection will ride over said cylindrical pin when the operating member is moved in the direction for releasing the clamp ing action of said clamping means.

5. In an electric switch including an insulating panel, a pair of spaced apart posts mounted on said panel, one of said posts constituting a fixed contact, a pair of movable contact blades pivoted at one end on the other of said posts and movable into and out of engagement with said fixed contact, clamping means at each of the opposite ends of said contact blades for exerting pressure between said blades and said posts in the switch closed position, and operating means including a connecting rod operatively connected between said clamping mean and movable longitudinally relative to said blades in one direction to effect the clamping action of said clamping means and in the opposite direction to release the clamping action; locking means, for preventing movement of said connecting rod in said one direction when said blades are in switch open position, comprising a fixed abutment carried by said connecting rod, stop means rockably carried by one of said blades and movable into and out of the path of travel of said abutment moving with said connecting rod, means constantly urging said stop means into the path of travel of said abutment to thereby prevent longitudinal movement of the latter in the direction for effecting the clamping action, and releasing means engaging said stop means when said blades are I swung to switch closed position and moving said stop means out of the path of travel of said abutment whereby said connecting rod may be moved to effect the clamping action or said clamping means, said stop means including a substantially triangular bell crank disposed between said pair of blades and pivoted at a corner thereof to one of said blades for swinging in a plane parallel to the planes of movement of the latter, said bell crank being formed with a lateral projection remote from the pivoted corner and disposed beyond the side edges of said blades for engagement with said abutment on said connecting rod.

6. In an electric switch, locking means according to claim 5, wherein said means constantly urging said stop means into the path of travel of said abutment includes a spring member interposed between said bell crank and one of said blades constantly urging said bell crank to rock in the direction of movement of said blades in travelling to switch closed position, and adjustable means carried by one of said blades and engaging said bell crank for limiting the movement of said bell crank in the spring urged direction.

7. In an electric switch, locking means according to claim 6, wherein said bell crank is formed with a recess in the edge thereof opposite from the pivoted corner, and said adjustable means is constituted by an eccentric cam member loosely received by said recess and rotatably mounted on one of said blades, said eccentric cam member engaging a portion of the edge of said recess to thereby limit movement of said bell crank in the spring urged direction.

8. In an electric switch, locking means according to claim 7, wherein said abutment fixed to said connecting rod consists of an elongated cylindrical pin extending laterally from the side of said operating member facing said bell crank.

9. In an electric switch, locking means according to claim 8, wherein said lateral projection on said bell crank extends towards said connecting rod and is inclined relative to the path of travel of said cylindrical pin with said connecting rod so that said projection will ride over said pin when the connecting rod is moved in the direction for releasing the clamping action of said clamping means.

FRED E. LUEBKERT.

References Cited in the file of this patent UNITED STATES PATENTS 

